Work machines, such as an articulated wheel loader, are configured to lift, move, and dump or place loads. Hydraulic pressure is used to lift and dump the loads. In particular, a hydraulically actuated lift cylinder or pair of lift cylinders act upon a lift arm in order to raise and lower the arm lift arm and a work implement attached thereto. A hydraulically actuated tilt cylinder or pair of cylinders is used to position the work implement to receive or dump loads.
The most common loads that the articulated wheel loader hauls and moves are dirt, rock, and other dense material. The lifting of these types of materials requires that the articulated wheel loader is configured to lift the dense load to a height necessary for dumping the load into a standard dump truck.
However, for some applications, a wheel loader is required to lift a less dense load to a greater height. Typically, these loads includes agricultural products or waste products which require the lift arm to lift the work implement to a greater height in order to dump loads into high sided wagons or hoppers typically used in agricultural and waste handling applications.
One solution to increasing the lift and dump height of a standard lift arm is to extend an existing lift arm. This allows the same hydraulic cylinders to lift a load to a greater height. A drawback associated with extending the lift arm is decreased stability of the wheel loader. As a load is lifted, the arm moves through a point of maximum instability where the load exerts a maximum moment, i.e. the weight of the load multiplied by distance to the load, about a front axle of the work machine. This maximum moment can cause the work machine to overturn about the front axle. By increasing the distance to the load with the extended lift arm, the maximum moment increases, which increases the maximum instability of the work machine. Thus, the stability of the work machine becomes a limiting factor in the configuration of the extended lift arm.
Alternately, the length of the hydraulic lift cylinders could be increased, allowing the work machine to lift the load to a greater height with the existing lift arm. A drawback to increasing the length of the hydraulic cylinders is that longer cylinders are more likely to buckle and longer cylinders may have to be repositioned on the work machine. Furthermore, hydraulic cylinders are expensive to manufacture thereby making the upgrade to an extended lift height a costly proposition.
What is needed therefore is an extended height lift arm for a work machine which overcomes one or more of the above-mentioned drawbacks.